Abstract
Elemental composition has been measured in aerosol samples as a function of time continuously during summer 1976 at land-based sites in the U.S.A. close to the Great Lakes. A 14-station network was employed to determine variations with 2-hour time resolution. Each sampling device produced a 7-day time dependent sample streak on 0.4 μm pore diameter Nuclepore filters at 0.60 liter/min flowrates by a slowly sliding sucking orifice. Analysis for S, Cl, K, Ca, Fe, Br, Pb and 8 other elements of Z ≥ 15 was performed by proton-induced X-ray emission by moving the sample frame across a 5 MeV proton beam from a tandem Van de Graaff accelerator in 84 individual time steps. Sulfur and many trace elements exhibit marked time variations without strong inter-site correlations. Inter-element correlations, e.g. at the Argonne National Laboratory site, indicate that the time variation pattern of sulfur differs from those of soil-derived K, Ca, and Fe and also from anthropogenically derived Pb and Br. Long range transport of elements from sources in the northeast portion of the U.S. appears likely. The transport of pollution-derived sulfur especially could have a significant effect on water quality in the Great Lakes as well as on precipitation pH levels in the Great Lakes basin.
Published Version
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